Xuchao Wang

The microstructure and magnetic properties of melt-spun CeFeB ribbons with varying Ce content

The microstructural and magnetic properties of melt-spun ribbons with the composition (CexNd100-x)30FebalCo4Ga0.2B0.92 (where x = 50, 60, 70, 80, and 90) were investigated. The ribbons were examined with Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), and Vibrating Sample Magnetometry (VSM). It was found that the grain size of the ribbons is on the nanometer scale, and the grain size decreases with decreasing Ce content. The magnetic hysteresis loops showed that the magnetic properties of the ribbons gradually deteriorated with increasing Ce content. This is because the magnetic polarization (Js) and magnetocrystalline anisotropy field (HA) of Ce2Fe14B are smaller than those of Nd2Fe14B. Furthermore, from the initial magnetization curve it was found that increasing the Ce content changes the coercive force mechanism to the nucleation mechanism. When Ce content accounts for 90% of total rare earth metals, the coercive force mechanism mainly appears to be a nucleation mechanism.

Microstructure and Properties of Die-Upset Nd-Fe-B/Dy

Fabrication of rare-earth-based permanent magnets with both high electrical resistivity and excellent magnetic properties for the traction motor applications is highly challenging. In this paper, Nd-Fe-B/Dy2O3 composite magnets have been fabricated by hot-pressing and die-upset. The influence of Dy2O3 filler on the microstructures, electrical resistivity and magnetic properties of the Nd-Fe-B magnets have been investigated by scanning electron microscope, four-probe resistivity meter and hysteresis graph. The results showed that the electrical resistivities of the Nd-Fe-B/Dy2O3 composite magnets increased with the increase of Dy2O3 amount and reached 1270 cm when the Dy2O3 amount increased to 20 wt.%. Whereas the electrical resistivity of the nondoped Nd-Fe-B magnets is 230 cm. The cross-section SEM images of the composite magnets showed that the Dy O phase formed laminated structure and some agglomerate phenomenon. The agglomerate areas became larger with the increase of Dy2O3 amount. The residual magnetic flux density and maximum energy product of the Nd-Fe-B/Dy2O3 composite magnets decreased due to the nonmagnetic Dy2O3 filler. It is interesting to find that coercivity of the Nd-Fe-B/Dy2O3 composite magnets increased from 7.8 kOe to 9.64 kOe when the Dy O amount increased from 10 wt.% to 20 wt.%. The reason may be that some of the dysprosium diffused into the Nd-Fe-B matrix and formed (Nd,Dy)2Fe14B compounds. In the mean time, some of neodymium-rich phase diffused to Dy2O3 phase, replaced dysprosium and formed Nd O . This probably happened during the die-upset process at 850°C.